The field of the invention is a deep-drawing tool.
The state of the art here is a deep-drawing tool which consists essentially of a punch, a holding-down device and a deep-drawing die.
In these prior art deep-drawing tools, the holding-down device is movable separately from the punch and is intended to sit on the metal sheet to be deep drawn and to hold this metal sheet down, while the punch moves simultaneously downward and pushes the metal sheet into the deep-drawing die, shaping it.
With the prior art holding-down devices, there is the disadvantage that holding-down devices are made of a metal which is impacted by a press of its own such that this metal sheet is held down with a relatively high pressure.
The design of the holding-down device with a press of its own (press punch) has, however, the disadvantage that the tool is very expensive and very costly to produce.
The object of the invention is thus to more economically produce a deep-drawing tool of the type mentioned at the beginning.
To achieve the object established, the invention is characterized by the technical teachings of claim 1.
An essential characteristic of the invention is that the holding-down device""s is incorporated into the punch of the deep-drawing tool and is not impacted by a separate punch.
Provision is made in an improvement of the invention that the holding-down device is designed not as a ring, but rather that the holding-down device consists of individual punches disposed uniformly distributed on the circumference, which punches are designed as elastomers.
They are thus spring punches which preferably are made of an elastomeric material which has high resilience. Resilient attachment of the holding-down device is alternatively or additionally possible.
With it, the significant advantage is obtained that it is possible to do without a punch drive for the holding-down device, since according to the invention the holding-down device disposed in the punch itself. It has now been discovered that certain materials for the holding-down devices are best suited to generate an appropriate retaining force on the metal sheet to be secured, whereby this material is so highly deformable that with a simultaneously secured metal sheet (with a high hold-down pressure), the punch can penetrate into the necessary forming path in the die.
A polyurethane foam with a high resilience, of, for example, 50%, is preferably used as a material for the elastic body.
A plastic material which is adjustable with differing holding characteristics according to requirements is preferably used as the material for the brake shoes. Thus, for example, a polyethylene, a polyurethane, or the like may be used as the plastic material. Depending on the material used, a specific coefficient of friction is obtained upon contact with the metal sheet to be held.
The use of interchangeable cylindrical holding-down devices yields the significant advantage that according to requirements the holding-down devices, which are designed according to the invention as punches, are held interchangeably.
Thus, the type of holding-down device may be changed for a complex shaped deep-drawn part, in that, for example, holding-down devices with high resilience may be used on one side and holding-down devices with low resilience may be used on the other, such that high tension and thus a high retaining force is exerted on the deep-drawn part on the side with the holding-down devices with low resilience, whereas a lower retaining force is exerted on the deep-drawn part on the opposite side where the holding-down devices with high resilience are used.
In an additional embodiment of the invention, provision is made that the holding-down device is also provided with brake shoes, which brake shoes adapt to the deep-drawn part.
Thus, it is possible to alter the type and design of the brake shoes.
In a first embodiment, provision is made that each holding-down device (which is designed as a punch) is coordinated with its own brake shoe, which shoe corresponds to the cross-section of the holding-down device.
In another embodiment of the invention, provision is made that the brake shoe is designed as a surrounding ring on which the holding-down devices sit distributed piece by piece on the circumference. The retentive force may be altered by changing the type of material and the dimensions and the holding-down devices. For this, it is important that the brake shoes be able to elastically change shape slightly in order to be able to adapt to the surrounding edge of the deep-drawn part.
In the technical teaching reported, deep-drawing machines may thus be built very economically since it is possible to completely do without a dedicated drive for the holding-down device.
The object of the present invention results not only from the object of the individual claims but also from the combination of the individual claims with each other. All information and characteristics disclosed in the documents, including the abstract, in particular the spatial design depicted in the drawings are claimed as essential to the invention, to the extent they are new individually/or in combination compared to the state of the art.